Echo suppression

ABSTRACT

Method, user device and computer program product for suppressing echo. An audio signal is output from a speaker. A microphone receives an audio signal, wherein the received audio signal includes an echo resulting from the outputted audio signal. A Finite Impulse Response filter estimate ĥ(n) is dynamically adapted in the time domain based on the outputted audio signal and the received audio signal to model an echo path h(n) related to the echo in the received audio signal. The filter estimate ĥ(n) is used in an estimate of the echo power in the received audio signal, and the estimated echo power is used to apply echo suppression to the received audio signal, thereby suppressing the echo in the received audio signal.

RELATED APPLICATION

This application claims priority under 35 USC 119 or 365 to GreatBritain Application No. 1223246.8 filed Dec. 21, 2012, the disclosure ofwhich is incorporate in its entirety.

BACKGROUND

A device may have audio input apparatus that can be used to receiveaudio signals from the surrounding environment. The device may also haveaudio output apparatus that can be used to output audio signals to thesurrounding environment. For example, a device may have one or morespeakers for outputting audio signals and one or more microphones forreceiving audio signals. Audio signals which are output from thespeaker(s) of the device may be received as “echo” in the audio signalreceived by the microphone(s). It may be the case that this echo is notdesired in the received audio signal. For example, the device may be auser device (such as a mobile phone, tablet, laptop, PC, etc) which isused in a communication event, such as an audio or video call, withanother user device over a network. Far-end signals of the call may beoutput from the speaker at the user device and may be received as echoin the audio signals received by the microphone at the device. Such echocan be disturbing to users of the call, and the perceived quality of thecall may be reduced due to the echo. In particular, the echo may causeinterference for near-end audio signals which are intended to bereceived by the microphone and transmitted to the far-end in the call.Therefore echo cancellation and/or echo suppression may be applied tothe received audio signals to thereby suppress the echo in the receivedaudio signal. The power of the echo in the received audio signal mayvary depending upon the arrangement of the user device. For example, theuser device may be a mobile phone and in that case, the power of theecho in the received audio signal would normally be higher when themobile phone is operating in a “hands-free” mode compared to when themobile phone is not operating in a “hands-free” mode.

Echo cancellation (or “echo subtraction”) techniques aim to estimate anecho signal included in the audio signal received at the microphone,based on knowledge of the audio signal which is output from the speaker.The estimate of the echo signal can then be subtracted from the receivedaudio signal thereby removing at least some of the echo from thereceived audio signal. Echo suppression is used to applyfrequency-dependent suppression to the received audio signal to therebysuppress the echo in the received audio signal. In order for echosuppression to be implemented effectively, an echo suppressor needs tohave an accurate estimate of the power of the echo in the received audiosignal.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

There is provided a method of suppressing echo in a received audiosignal. As part of the echo suppression, an estimate of the echo powerof the echo is determined using a Finite Impulse Response (FIR) filterthat is adapted to approximate the impulse response of the echo path.That is, a Finite Impulse Response filter estimate ĥ(n) is dynamicallyadapted in the time domain based on the outputted audio signal and thereceived audio signal to thereby model the impulse response of the echopath h(n) of the echo in the received audio signal. The filter estimateĥ(n) is used to estimate the echo power of the echo in the receivedaudio signal, and the estimated echo power is used to apply echosuppression to the received audio signal, thereby suppressing the echoin the received audio signal.

The method may be used in a call (e.g. a call implementing voice overinternet protocol (VoIP) to transmit audio data between user devices) inwhich case the outputted audio signal may be a far-end signal receivedfrom the far-end of the call, and the received signal includes theresulting echo and a near-end signal for transmission to the far-end ofthe call.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic illustration of a communication system inaccordance with one or more embodiments;

FIG. 2 is a schematic block diagram of a user device in accordance withone or more embodiments;

FIG. 3 is a functional diagram showing modules of a user device for usein echo suppression in accordance with one or more embodiments; and

FIG. 4 is a flow chart for a process of suppressing echo in accordancewith one or more embodiments.

DETAILED DESCRIPTION

In order for echo suppression to be implemented effectively, an echosuppressor needs to have an accurate estimate of the power of the echoin the received audio signal. As described herein, the echo power can beestimated using the output from a FIR filter that is adapted toapproximate the impulse response of the echo path between a loudspeakeroutputting audio signals and a microphone receiving audio signalsincluding the echo resulting from the outputted audio signals.

The FIR filter might only be used to estimate the echo power, and not toestimate the actual echo signal. This may be advantageous because therequirements for accuracy in the FIR filter are much less when used toestimate the echo power compared to if the FIR filter is used toestimate the actual echo signal. Therefore by estimating the echo power(rather than the echo signal) from the FIR filter, echo suppression ismore robust to problems such as clock-drift between the playout (e.g.from a loudspeaker) and recording sides (e.g. at a microphone) in theVoIP client, nonlinearities in the echo path and changes in the echopath. In embodiments described herein, the FIR filter is adapted usingtime-domain data including phase information.

FIG. 1 shows a communication system 100 comprising a first user 102(“User A”) who is associated with a first user device 104 and a seconduser 108 (“User B”) who is associated with a second user device 110. Inother embodiments the communication system 100 may comprise any numberof users and associated user devices. The user devices 104 and 110 cancommunicate over the network 106 in the communication system 100,thereby allowing the users 102 and 108 to communicate with each otherover the network 106. The communication system 100 shown in FIG. 1 is apacket-based communication system, but other types of communicationsystem could be used. The network 106 may, for example, be the Internet.Each of the user devices 104 and 110 may be, for example, a mobilephone, a tablet, a laptop, a personal computer (“PC”) (including, forexample, Windows™, Mac OS™ and Linux™ PCs), a gaming device, atelevision, a personal digital assistant (“PDA”) or other embeddeddevice able to connect to the network 106. The user device 104 isarranged to receive information from and output information to the user102 of the user device 104. The user device 104 comprises output meanssuch as a display and speakers. The user device 104 also comprises inputmeans such as a keypad, a touch-screen, a microphone for receiving audiosignals and/or a camera for capturing images of a video signal. The userdevice 104 is connected to the network 106.

The user device 104 executes an instance of a communication client,provided by a software provider associated with the communication system100. The communication client is a software program executed on a localprocessor in the user device 104. The client performs the processingrequired at the user device 104 in order for the user device 104 totransmit and receive data over the communication system 100.

The user device 110 corresponds to the user device 104 and executes, ona local processor, a communication client which corresponds to thecommunication client executed at the user device 104. The client at theuser device 110 performs the processing required to allow the user 108to communicate over the network 106 in the same way that the client atthe user device 104 performs the processing required to allow the user102 to communicate over the network 106. The user devices 104 and 110are endpoints in the communication system 100. FIG. 1 shows only twousers (102 and 108) and two user devices (104 and 110) for clarity, butmany more users and user devices may be included in the communicationsystem 100, and may communicate over the communication system 100 usingrespective communication clients executed on the respective userdevices.

FIG. 2 illustrates a detailed view of the user device 104 on which isexecuted a communication client instance 206 for communicating over thecommunication system 100. The user device 104 comprises a centralprocessing unit (“CPU”) or “processing module” 202, to which isconnected: output devices such as a display 208, which may beimplemented as a touch-screen, and a speaker (or “loudspeaker”) 210 foroutputting audio signals; input devices such as a microphone 212 forreceiving audio signals, a camera 216 for receiving image data, and akeypad 218; a memory 214 for storing data; and a network interface 220such as a modem for communication with the network 106. The user device104 may comprise other elements than those shown in FIG. 2. The display208, speaker 210, microphone 212, memory 214, camera 216, keypad 218 andnetwork interface 220 may be integrated into the user device 104 asshown in FIG. 2. In alternative user devices one or more of the display208, speaker 210, microphone 212, memory 214, camera 216, keypad 218 andnetwork interface 220 may not be integrated into the user device 104 andmay be connected to the CPU 202 via respective interfaces. One exampleof such an interface is a USB interface. If the connection of the userdevice 104 to the network 106 via the network interface 220 is awireless connection then the network interface 220 may include anantenna for wirelessly transmitting signals to the network 106 andwirelessly receiving signals from the network 106.

FIG. 2 also illustrates an operating system (“OS”) 204 executed on theCPU 202. Running on top of the OS 204 is the software of the clientinstance 206 of the communication system 100. The operating system 204manages the hardware resources of the computer and handles data beingtransmitted to and from the network 106 via the network interface 220.The client 206 communicates with the operating system 204 and managesthe connections over the communication system. The client 206 has aclient user interface which is used to present information to the user102 and to receive information from the user 104. In this way, theclient 206 performs the processing required to allow the user 102 tocommunicate over the communication system 100.

With reference to FIGS. 3 and 4 there is now described a method ofsuppressing echo. FIG. 3 is a functional diagram of a part of the userdevice 104 showing how an echo suppression process is implemented, andFIG. 4 is a flow chart for the process of suppressing echo.

As shown in FIG. 3, the user device 104 comprises the speaker 210, themicrophone 212, a FIR filter module 302, a power estimating module 304and an echo suppression module 306. A signal x(t) to be output from thespeaker 210 is coupled to an input of the speaker 210. It should benoted that in the embodiments described herein there is just oneloudspeaker (indicated by reference numeral 210 in the figures) but inother embodiments there may be more than one loudspeaker to which thesignal to be outputted is coupled (for outputting therefrom). Similarly,in the embodiments described herein there is just one microphone(indicated by reference numeral 212 in the figures) but in otherembodiments there may be more than one microphone which receive audiosignals from the surrounding environment. The signal to be output fromthe loudspeaker 210 is also coupled to a first input of a FIR filtermodule 302 and to a first input of the power estimating module 304. Anoutput of the microphone 212 is coupled to a second input of the FIRfilter module 302 and to a first input of the echo suppression module306. An output of the FIR filter module 302 is coupled to a second inputof the power estimating module 304. An output of the power estimatingmodule is coupled to a second input of the echo suppression module 306.An output of the echo suppression module 306 is used to provide thereceived signal (with echo suppression having been applied) for furtherprocessing in the user device 104.

In step S402 a signal is received which is to be outputted from thespeaker 210. For example, the signal to be outputted may be a far-endsignal that has been received at the user device 104 from the userdevice 110 during a call between the users 102 and 108 over thecommunication system 100. Any processing that is required to beperformed on the received signal (e.g. decoding using a speech codec,depacketizing, etc) is performed as is known in the art (e.g. by theclient 206) to arrive at the signal x(t) which is suitable to beoutputted from the speaker 210. The signal x(t) is a digital signal. Atleast some of the processing of the signal in the user device 104 priorto outputting the signal from the speaker 210 is performed in thedigital domain. As is known in the art, a digital to analogue converter(DAC) is applied to the digital signal x(t) before playout from theloudspeaker 210. Similarly, an analogue to digital converter (ADC) isapplied to the signal captured by the microphone 212 to arrive at thedigital signal y(t).

In other embodiments, the signal to be outputted may be received fromsomewhere other than over the communication system 100 in a call. Forexample, the signal to be outputted may have been stored in the memory214 and step S402 may comprise retrieving the signal from the memory214.

In step S404 the audio signal x(t) is outputted from the speaker 210. Inthis way the audio signal x(t) is outputted to the user 102.

In step S406 the microphone 212 receives an audio signal. As shown inFIG. 3 the received audio signal may include a near-end signal which isa desired signal or “primary signal”. The near-end signal is the signalthat the user 102 intends the microphone 212 to receive. However, thereceived audio signal also includes an echo signal resulting from theaudio signals outputted from the speaker 210 in step S404. The receivedaudio signal may also include noise, such as background noise.Therefore, the total received audio signal y(t) can be given by the sumof the near-end signal, the echo and the noise. The echo and the noiseact as interference for the near-end signal.

The FIR filter module 302 takes as inputs the outputted audio signalx(t) and the received audio signal y(t). In step S408 the FIR filtermodule 302 dynamically adapts a FIR filter estimate ĥ(n) in the timedomain based on the outputted audio signal x(t) and the received audiosignal y(t) to model an echo path h(n) of the echo in the received audiosignal y(t). The “impulse response of the echo path h(n)” is alsoreferred to herein as the “echo path h(n)”.

For a linear echo path impulse response of length N_(true)+1 the echopath h(n) describes how the echo in the received audio signal relates tothe audio signal x(t) output from the speaker 210, e.g. according to theequation y_(echo)(t)=Σ_(n=0) ^(N) ^(tru) h(n)×(t−n), where y_(echo) (t)is the echo in the received audio signal y(t). The echo path h(n) mayvary over time. The echo path h(n) may depend upon (i) the currentenvironmental conditions surrounding the speaker 210 and the microphone212 (e.g. whether there are any physical obstructions to the passage ofthe audio signal from the speaker 210 to the microphone 212, the airpressure, temperature, wind, etc), and (ii) characteristics of thespeaker 210 and/or the microphone 212 which may alter the signal as itis outputted and/or received.

The FIR filter module 302 models the echo path h(n) of the echo in thereceived audio signal by determining a weighted sum of the current and afinite number (N) of previous values of the outputted audio signal x(t).The FIR filter module 302 therefore implements an Nth order FIR filterwhich has a finite length (in time) over which it considers the valuesof the outputted audio signal x(t) in determining the estimate of theecho path ĥ(n). In this way, the FIR filter module 302 dynamicallyadapts the FIR filter estimate ĥ(n). The operation is described by thefollowing equation, which defines the echo in the received audio signaly(t) in terms of the outputted audio signal x(t):ŷ ^(echo)(t)=Σ_(n=0) ^(N) ĥ(n)x(t−n).Therefore N+1 samples of the outputted audio signal x(t) are used, witha respective N+1 weights ĥ(n). The set of N+1 weights ĥ(n) is referredto herein simply as the estimate of the echo path ĥ(n). In other wordsthe estimate of the echo path ĥ(n) consists of N+1 values where the FIRfilter module 302 implements an Nth order FIR filter, taking N+1 values(e.g. N+1 samples) of the signal x(t) into account.

It can be appreciated that it is easier to adapt the FIR filter estimateĥ(n) when the echo is a dominant part of the received audio signal, thatis when y(t)≅y^(echo)(t). For example, in some embodiments it may bepossible to detect when the power of the near-end signal is greater thanthe power of the echo (e.g. when the user 102 is speaking), and whilstthat is the case the FIR estimate ĥ(n) is not adapted, but when thepower of the near-end signal is less than the power of the echo in thereceived audio signal y(t) (e.g. when the user 102 is not speaking) theFIR estimate ĥ(n) is adapted.

However, it may be possible to adapt the FIR filter estimate ĥ(n) evenwhen the echo is not a dominant part of the received audio signal. Forexample, if the adaptation is slower, there is a gain in robustness todisturbances.

The FIR filter estimate ĥ(n) is passed from the FIR filter module 302 tothe power estimating module 304. In step S410 the power estimatingmodule 304 estimates the echo power of the echo in the received audiosignal based on the filter estimate ĥ(n) determined in step S408. StepS410 might not comprise estimating the echo signal ŷ^(echo)(t) in thereceived audio signal y(t). The echo power is estimated as a function oftime and frequency. Using the estimated echo path ĥ(n) and the inputsignal x(t) to estimate the echo power for an echo suppressor is muchless sensitive to inaccuracies in the FIR filter approximation of theecho path, than using an estimate of the echo signal ŷ^(echo)(t) for anecho subtractor/canceller. For example, the usage of the estimate of theecho path ĥ(n) provided by the FIR filter module 302 and the inputsignal x(t) for echo power estimation is much less sensitive to problemssuch as clock-drift between the playout and recording sides on the localendpoint, suboptimal FIR filter updates, nonlinearities in the echopath, and time-variations in the echo path. In echo suppression a ratherlow accuracy of the echo power estimate is sufficient to achieve goodecho suppression. In this way, a linear filter is used for estimating apower spectrum used for echo suppression. This is more robust than usinga linear filter for estimating a time domain echo signal for an echosubtractor.

Step S410 may comprise estimating the echo power {circumflex over(P)}_(s)(t, f), which is a scalar power bin for time t and frequency f.This can be calculated using the Fourier transform, as known by peopleskilled in the art.

In this way, the FIR filter estimate ĥ(n), that has been adapted usingthe speaker and microphone signals x(t) and y(t) to approximate thetime-varying echo path h(n) of the VoIP client, is used, with theoutputted audio signal samples x(t), to estimate the power {circumflexover (P)}_(s)(t, f) of the echo signal at time t and frequency f.

The estimate of the echo power {circumflex over (P)}_(s)(t, f) is outputfrom the power estimating module 304 and received by the echosuppression module 306. The echo suppression module 306 also receivesthe audio signal y(t) from the microphone 212. In step S412 the echosuppression module 306 uses the estimate of the echo power {circumflexover (P)}_(s)(t, f) to apply echo suppression to the received audiosignal y(t), thereby suppressing the echo in the received audio signal.The estimate of the echo power {circumflex over (P)}_(s)(t, f) isfrequency dependent and the suppression applied by the echo suppressionmodule 306 is also frequency dependent.

The purpose of the echo suppressor is to suppress the loudspeaker echopresent in the microphone signal, e.g. in a VoIP client, to a levelsufficiently low for it not to be noticeable/disturbing in the presenceof the near-end sounds (non-echo sounds) picked up by the microphone212. In order to be able to choose the proper amount of echo suppressiona good estimate of the echo power (e.g. as a function of frequency andtime) is needed, and as described above this is provided to the echosuppression module 306 by the power estimating module 304. The echosuppression module 306 is designed to apply signal dependent suppressionthat varies both over time and frequency to the received audio signaly(t). Echo suppression methods are known in the art. Furthermore, theecho suppression method applied by the echo suppression module 306 maybe implemented in different ways. As such, the exact details of the echosuppression method are therefore not described in detail herein.

The echo suppression module 306 outputs the received signal, with theecho having been suppressed, for further processing at the user device104. For example, the signal output from the echo suppression module 306may be processed by the client 206 (e.g. encoded and packetized) andthen transmitted over the network 106 to the user device 110 in a callbetween the users 102 and 108. Additionally or alternatively, the signaloutput from the echo suppression module 306 may be used for otherpurposes by the user device 104, e.g. the signal may be stored in thememory 214 or used as an input to an application which is executing atthe user device 104.

There is therefore described herein the use of an FIR filter module 302to model the echo path to estimate the power of the loudspeaker echosignal picked up by the microphone 212, for the purpose of computing andapplying an echo suppression effect/filter (e.g. for use by the VoIPclient 206).

In the embodiments described above, the echo suppression is implementedin a VoIP system (e.g. the received audio signal may include speech ofthe user 102 for transmission to the user device 110 during a callbetween the users 102 and 108 over the communication system 100).However, the echo suppression methods described herein can be applied inany suitable system in which echo suppression is to be applied.

In the embodiments described above, and shown in the Figures, echocancellation (or “echo subtraction”) is not applied to the receivedaudio signal y(t). That is, there is no echo cancellation module in theuser device 104 and the echo suppression is applied to the receivedaudio signal y(t) without a prior step of applying echo cancellation tothe received audio signal y(t).

However, in other embodiments, echo cancellation may be applied, by anecho cancellation module, to the received audio signal y(t). Inparticular, the echo suppression applied by the echo suppression module306 may be applied downstream (i.e. after) of the echo cancellation inthe processing of the received audio signal y(t). The echo cancellationmodule would subtract an estimate of the echo signal from the receivedaudio signal, but due to inaccuracies in the estimate of the echosignal, a residual echo would most-likely remain in the received audiosignal. It is the residual echo that would then be suppressed by theecho suppression module 306. This echo suppression could be applied inthe same way as described herein in the embodiments in which no echocancellation is applied. If echo subtraction is used, the effect of it,would be taken into account in the echo suppression.

The methods described herein may be implemented by executing a computerprogram product (e.g. the client 206) at the user device 104. That is, acomputer program product may be configured to suppress echo in thereceived audio signal y(t), wherein the computer program product isembodied on a computer-readable storage medium (e.g. stored in thememory 214) and configured so as when executed on the CPU 202 to performthe operations of any of the methods described herein. The term“computer-readable storage medium” is intended to cover all statutoryforms of media and thus excludes non-statutory forms of media.

Generally, any of the functions described herein (e.g. the functionalmodules shown in FIG. 3 and the functional steps shown in FIG. 4) can beimplemented using software, firmware, hardware (e.g., fixed logiccircuitry), or a combination of these implementations. The modules andsteps shown separately in FIGS. 3 and 4 may or may not be implemented asseparate modules or steps. For example, the echo suppression module 306may perform the function of the power estimating module 304, such that aseparate power estimating module 304 is not required in addition to theecho suppression module 306. The terms “module,” “functionality,”“component” and “logic” as used herein generally represent software,firmware, hardware, or a combination thereof. In the case of a softwareimplementation, the module, functionality, or logic represents programcode that performs specified tasks when executed on a processor (e.g.CPU or CPUs). The program code can be stored in one or more computerreadable memory devices. The features of the techniques described hereinare platform-independent, meaning that the techniques may be implementedon a variety of commercial computing platforms having a variety ofprocessors.

For example, the user devices may also include an entity (e.g. software)that causes hardware of the user devices to perform operations, e.g.,processors functional blocks, and so on. For example, the user devicesmay include a computer-readable medium that may be configured tomaintain instructions that cause the user devices, and more particularlythe operating system and associated hardware of the user devices toperform operations. Thus, the instructions function to configure theoperating system and associated hardware to perform the operations andin this way result in transformation of the operating system andassociated hardware to perform functions. The instructions may beprovided by the computer-readable medium to the user devices through avariety of different configurations.

One such configuration of a computer-readable medium is signal bearingmedium and thus is configured to transmit the instructions (e.g. as acarrier wave) to the computing device, such as via a network. Thecomputer-readable medium may also be configured as a computer-readablestorage medium and thus is not a signal bearing medium. Examples of acomputer-readable storage medium include a random-access memory (RAM),read-only memory (ROM), an optical disc, flash memory, hard disk memory,and other memory devices that may us magnetic, optical, and othertechniques to store instructions and other data.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

The invention claimed is:
 1. A method of suppressing echo, the methodcomprising: outputting an audio output signal; receiving an audio inputsignal, wherein the received audio input signal includes an echoresulting from the outputting the audio output signal; dynamicallyadapting a Finite Impulse Response filter estimate ĥ(n) in the timedomain, based on the audio output signal and the received audio inputsignal, to model an echo path h(n) of the echo in the received audioinput signal; estimating an echo power in the received audio inputsignal using the filter estimate ĥ(n) and the audio output signal; andsuppressing the echo in the received audio input signal based on theestimated echo power.
 2. The method of claim 1 wherein the suppressingthe echo is performed on the received input audio signal withoutapplying echo cancellation to the received audio input signal prior tothe suppressing the echo.
 3. The method of claim 1 further comprisingapplying echo cancellation to the received audio input signal prior tothe suppressing the echo, wherein the suppressing the echo suppressesresidual echo remaining in the received audio signal after the appliedecho cancellation.
 4. The method of claim 1 wherein the suppressing theecho is signal-dependent suppression that varies over time andfrequency.
 5. The method of claim 1 wherein the method is performed at auser device for use in a communication event, and wherein the receivedaudio input signal comprises speech of a user for transmission from theuser device in the communication event.
 6. The method of claim 5 whereinthe communication event is a voice-over-internet-protocol (VoIP) call.7. The method of claim 6 wherein the audio output signal comprisesfar-end speech signals of the VoIP call which are included in the echoin the received audio input signal.
 8. The method of claim 1 wherein theaudio output signal is output from a speaker and the received audioinput signal is received by a microphone.
 9. A device configured toimplement echo suppression, the device comprising: an audio outputapparatus configured to output an audio output signal; an audio inputapparatus configured to receive an audio input signal, wherein thereceived audio input signal includes an echo resulting from the outputof the audio output signal; a filter estimating module configured todynamically adapt a Finite Impulse Response filter estimate ĥ(n) in thetime domain, based on the audio output signal and the received audioinput signal, to model an echo path h(n) related to the echo in thereceived audio input signal; a power estimating module configured toestimate an echo power in the received audio input signal based on thefilter estimate ĥ(n) and the audio output signal; and an echosuppression module configured to suppress the echo in the received audioinput signal.
 10. The device of claim 9 wherein the audio outputapparatus comprises a speaker configured to output the audio outputsignal, and wherein the audio input apparatus comprises a microphoneconfigured to receive the audio input signal.
 11. The device of claim 9wherein the device does not comprise an echo cancellation moduleconfigured to apply echo cancellation to the received audio inputsignal.
 12. The device of claim 9 further comprising an echocancellation module configured to apply echo cancellation to thereceived audio input signal prior to the suppression of the echo by theecho suppression module, wherein the suppression of the echo suppressesresidual echo remaining in the received audio signal after the appliedecho cancellation.
 13. The device of claim 9 wherein the device is auser device useable by a user and wherein the device is configured foruse in a communication event, the user device further comprising atransmission module configured to transmit the echo-suppressed receivedaudio input signals from the user device in the communication event. 14.The device of claim 13 wherein the communication event is avoice-over-internet-protocol (VoIP) call.
 15. The device of claim 14wherein the audio output signal comprises far-end speech signals of theVoIP call which are included in the echo in the received audio inputsignal.
 16. The device of claim 9 wherein the suppression of the echosignal-dependent suppression that varies over time and frequency.
 17. Asystem configured to suppress echo in a received audio signal, thesystem comprising: a processor; and a computer-readable storage memorycomprising instructions executable by the processor to performoperations comprising: outputting an audio output signal; receiving anaudio input signal, wherein the received audio input signal includes anecho resulting from said outputted the outputting the audio outputsignal; dynamically adapting a Finite Impulse Response filter estimateĥ(n) in the time domain, based on the outputted audio output signal andthe received audio input signal, to model an echo path h(n) of the echoin the received audio input signal; estimating an echo power in thereceived audio input signal using the filter estimate ĥ(n) and the audiooutput signal; and suppressing the echo in the received audio inputsignal based on the estimated echo power.
 18. The system of claim 17wherein the suppressing the echo is performed on the received audioinput signal without applying echo cancellation to the received audioinput signal prior to the suppressing the echo.
 19. The system of claim17, the instructions-further executable to perform operationscomprising: applying echo cancellation to the received audio inputsignal prior to the suppressing the echo, wherein the suppressing theecho suppresses residual echo remaining in the received audio signalafter the applied echo cancellation.
 20. The system of claim 17, whereinthe received audio input signal comprises speech of a user fortransmission from a user device in a communication event.